Patent GB-661196-A (GB)
Title: Process for the treatment of scrap leather
IPC: C14C13/02
Filed: 1949-01-21
Abstract: Scrap leather is treated to recover fats and a brown or yellow dye, by digesting the scrap leather with an alkali in an autoclave with steam under pressure, removing the solution obtained and treating it, after separation of liberated fats, with an acid, particularly nitric acid, either (a) for a period of 1 or more hours to obtain after neutralizing a "leather solution," or (b) filtering off the solids obtained, followed by washing, neutralizing and vacuum drying the solids to obtain a brown dye, or (c) treating the "leather solution" obtained as in (a) with further acid, particularly nitric acid, and proceeding as in (b), to obtain a yellow dye, fats being also separated off during or after the acid treatment.  In the first stage treatment with alkali, a proportion of water is mixed with the leather scraps, the alkali is either caustic soda or caustic potash, and the temperature, depending on the steam pressure, varies from 250 DEG  to 360 DEG  F.  The treatment is continued with agitation until a neutral or slightly alkaline solution, which is soluble in water, is obtained.  In the second stage treatment with acid according to the process (a) above, the solution obtained is fed into glass or enamelled containers equipped with stirring apparatus, allowed to cool to segregate fats which are removed and then treated with the acid whilst stirring for the period specified, the vapours developed being exhausted from the containers.  On completion the mass cools, more fat is segregated and is removed, and the solution is then neutralized and filtered to obtain the so-called "leather solution" which is capable of producing a hard filling for leather when dried. In the second stage treatment with acid according to the process (b) above, the solution obtained from the autoclave is filtered and then treated with the acid, which in this case may be H2SO4, when the solids are precipitated which are removed, washed, and dissolved in caustic soda or caustic potash.  This solution is then vacuum dried and the solids obtained pulverized to form a brown dye.  Preliminary to the first stage of the processes, the scrap leather may be treated in the autoclave with water only and steam under pressure.  On cooling, the surface layer of fats may be removed, and the undissolved scrap leather treated as in the main process.ALSO:Scrap leather is treated to recover fats therefrom and either for the production of a so-called "leather solution" for filling purposes &c. or for the production of a brown or yellow dye, by digesting the scrap leather with an alkali in an autoclave with steam under pressure, removing the solution obtained and treating it, after separation of liberated fats, with an acid, particularly nitric acid, either (a) for a period of 1 or more hours to obtain after neutralising a "leather solution," or (b) filtering off the solids obtained, followed by washing, neutralising and vacuum drying the solids to obtain a brown dye, or (c) treating the "leather solution" obtained as in (a) with further acid, particularly nitric acid, and proceeding as in (b) to obtain a yellow dye, fats being also separated off during or after the acid treatment.  In the first stage treatment with alkali, a proportion of water is mixed with the leather scraps, the alkali is either caustic soda or caustic potash, and the temperature, depending on the steam pressure varies from 250 DEG  to 360 DEG F.  The treatment is continued with agitation until a neutral or slightly alkaline solution, which is soluble in water, is obtained.  In the second stage treatment with acid according to the process (a) above, the solution obtained is fed into glass or enamelled containers equipped with stirring apparatus, allowed to cool to segregate fats which are removed, and then treated with the acid whilst stirring for the period specified, the vapours developed being exhausted from the containers.  On completion the mass cools, more fat is segregated and is removed, and the solution is then neutralised and filtered to obtain the so-called "leather solution" which is capable of producing a hard filling for leather when dried. In the second stage treatment with acid according to the process (b) above, the solution obtained from the autoclave is filtered and then treated with the acid, which in this case may be H2SO4, when the solids are precipitated which are removed, washed, and dissolved in caustic soda or caustic potash.  This solution is then vacuum dried and the solids obtained pulverized to form a brown dye.  Preliminary p  to the first stage of the processes, the scrap leather may be treated in the autoclave with water only and steam under pressure. On cooling, the surface layer of fats may be removed, and the undissolved scrap leather treated as in the main process.